ZERO TO THREE and Los Angeles County Department of Mental Health (LACDMH) collaborated and contracted to provide official DC:0-5[TM] clinical training and foundational infant and early childhood mental health training to clinicians from Los Angeles (LA) County, California, over the course of 3 years. This article describes this unique, multiyear clinical workforce development effort highlighting the specific training approaches and supports used, considerations for sustainability, DC:0-5 Expert Faculty reflections, and participants' feedback. The authors provide recommendations for possible replication of this intensive workforce development effort.